i. Field of the Invention
This invention relates to a bearing lubrication system for extension housings of automatic transmissions for motor vehicles.
ii. Description of the Prior Art
An extension housing which constitutes part of a vehicular transmission case on the side of the transmission output shaft has a bearing portion for supporting the output shaft along with necessary lubricative means including oil seal. However, since it is located at the rear end of a transmission, smooth rotation of the output shaft is often hindered by restricted and insufficient supply of lubricant oil to those parts which need lubrication, resulting in undesirable output losses. In addition, the insufficient supply of lubricant oil gives rise to problems such as deterioration of sliding parts due to increased frictional heat generation and degradations of other parts induced by deterioration of sliding parts.
For supplying lubricant oil to a bearing portion of an extension housing which supports an output shaft, it has been the conventional practice to distribute lubricant oil to inner wall surfaces of the extension housing through oil passages formed in the output shaft with the aid of centrifugal force, or to distribute the oil to the bearing portions along ribs or grooves formed on inner wall surfaces of the extension housing, mainly utilizing the drain oil of a governor valve as a lubricant oil. These methods of lubrication have the following drawbacks.
(a) The drain oil which is supplied through the oil passages in the output shaft is applied to the inner wall surfaces of the extension housing by the centrifugal force, so that it fails to reach the inner wall surfaces of the extension housing in low speed operations.
(b) The oil which is supplied to the bearing portions along grooves or ribs formed on the inner wall surfaces of the extension housing hardly distributed when the vehicle is in a forwardly inclined state or on a downhill.
(c) The drain oil from the governor valve is not supplied when the shift lever is in neutral, reverse and parking positions.
(d) The drain oil of the governor oil is leaked in a greater amount at high temperatures, while the supply of the lubricant along ribs becomes difficult at low temperatures due to increased viscosity of the oil.